1. Field of the Invention
This invention relates to height adjustment devices for doors on transit vehicles such as buses and trains. More particularly the invention relates to a door height adjustment device for positioning and moving a shaft and arm assembly of a door of a transit vehicle. Some vehicle doors have a single panel mounted at an outside edge of the door opening. Many vehicle doors have two panels, each mounted at opposite outside edges of the door opening. The panels usually swing outward or inward or a combination thereof to permit entrance or exit of passengers.
2. Description of Related Art
It is sometimes desirable to adjust the height of the door of a transit vehicle for installation, repair, maintenance or upgrades. Current methods of adjusting the height of transit vehicle doors usually require substantial disassembly of the door assembly and related linkages, which requires the expenditure of significant time and effort. Other current methods require the addition or removal shims or adjustment rings to adjust the height of a transit vehicle door. This is also disadvantageous as it requires the appropriate hardware, shims or adjustment rings to be on hand when the door heights adjustments are made. This can add significant inventory costs for a fleet of transit vehicles, especially if adjustments need to be done in the field away from a centralized maintenance location.
An example of a type of transit vehicle door the present invention is aimed at improving is disclosed in U.S. Pat. No. 7,017,974. However other types and designs of transit vehicle doors can benefit from the improvements of the present invention.